Antennas and antenna arrays, in particular in the form of stationary antenna arrangements for base stations in the mobile radio field, have been known for a long time. Corresponding antenna designs are described, for example, in DE 197 22 742 A1, DE 196 27 015 A1, U.S. Pat. No. 5,710,569 or WO 00/39894.
Antenna designs such as these generally have a vertically arranged reflector which can be provided with vertically running webs or edge sections on its two opposite faces on the left and right, with these webs or edge sections generally projecting forwards from the reflector plane. Since more than one antenna element arrangement is generally provided, they are arranged one above the other with a vertical offset.
These may be single-polarized antenna element devices, although they are generally dual-polarized antenna element devices, which can transmit and receive in two mutually orthogonal polarization planes. The antenna elements and antenna element groups are in this case preferably arranged such that the two mutually perpendicular polarization planes are aligned at angles of plus 45° and minus 45° to the horizontal (and thus to the vertical).
Antennas and antenna arrays are likewise known which can transmit and/or receive with single or dual polarization not only in one frequency band, but, in particular, in two frequency bands (or more). These are also referred to as dual-band antennas or multiband antennas.
Finally, antenna arrays are also known in which two or more antenna elements are arranged not only one above the other in the vertical direction (effectively in only one column of an antenna array), but in which at least two or even more vertically running columns are provided which are positioned horizontally alongside one another, with each of the antenna elements or antenna element groups which are arranged in a column one above the other generally being fed jointly.
As mentioned, the antenna elements may in this case be in the form of dipole antenna elements, that is to say individual dipoles, for example composed of dipole pairs which are joined together in a cruciform shape, or of dipoles which form a dipole square. Antenna elements which are similar to dipole squares can also be used and, from the electrical point of view, they behave in the same way as cruciform antenna elements. Dipole structures such as these, which are also referred to as vector antenna elements are known, for example, from the cited WO 00/39894. Furthermore, however, patch antenna elements can also be used, such as those which are known, for example from WO 02/50940 A2.
Depending on the configuration of the antenna elements, on the number of the antenna elements which are used in the vertical direction and, possibly, on the two or more antenna elements which are arranged offset with respect to one another in the horizontal direction, all of these antennas or antenna arrays have a quite specific main beam direction, which is generally aligned at right angles to the reflector plane.
Since, particularly in the mobile radio field, each base station antenna is associated with a specific cell in which the mobile radio communication is handled via the relevant base station antenna, it may be necessary for the size of the relevant cell to be adjusted so that it is variable. For this purpose, it is already known for antennas of this type to be provided such that the main beam direction can be set with a different down-tilt angle. In theory, this down-tilt angle can be produced by mechanical pivoting of the entire antenna arrangement, so that the entire antenna device together with the holder on which it is mounted, the reflector plate, the antenna elements which are arranged on its front face and the radome which surrounds the antenna arrangement are pivoted manually or by a motor or motors about a horizontal axis, such that the main beam direction is lowered to a greater or lesser extent.
According to a present-day generation of corresponding antenna devices, the different setting of the down-tilt angle is produced electrically by means of different phase controls. Different phase control of the antenna elements and antenna element groups which are arranged vertically one above the other allows an appropriately different down-tilt angle to be set without any mechanical pivoting movement, solely by means of the electrical phase control.
The illustrative non-limiting technology described herein uses very simple means to improve the adjustment capability of the main beam direction for a corresponding antenna arrangement, and, in particular, antenna arrays, which can be used as a stationary antenna device for the mobile radio field.
The illustrative non-limiting technology described herein provides a simple capability for setting a main beam direction alignment which is different in the horizontal plane for an antenna having at least one antenna element which is fitted in front of a reflector.
In principle, it is already known to provide a means for antenna arrays having at least two columns for setting the main beam direction differently in the horizontal plane, that is to say in the azimuth direction. This can also be achieved by different phase control of the antenna elements or antenna element groups which are located offset in the horizontal direction. However, this is not possible with a single-column array.
In principle, it would be feasible to rotate an entire antenna arrangement including an antenna mast. However, in this case, it would also be necessary to move the cables which generally lead into the radome interior on the lower face or are connected to a holding flange on the lower face of the radome. However, in this situation, rotation would be possible, for example, if a corresponding antenna housing, that is to say the so-called radome, were attached to a housing wall or to a mount at the rear in the form of a wall.
According to the exemplary non-limiting technology described herein, provision is now made that, despite the pivoting movement about a longitudinal and/or vertical axis, essentially only the reflector and one or more antenna elements and antenna element groups which are located in front of it are pivoted, but not the radome itself, which surrounds the entire antenna arrangement including the reflector. A pivoting shaft which runs in the longitudinal or vertical direction and is provided in the interior of the radome is thus provided in order to pivot only those electrical parts of the antenna which are required for reception and for transmission (that is to say the reflector and the antenna elements), without the radome being pivoted. The radome thus has a sufficiently large interior. The radome itself can also be mounted in the same way as a conventional antenna arrangement on, for example, a post in the form of a rod, that can just as well also be mounted on a wall of a house or the like, since the radome itself is not also pivoted, even during horizontal pivoting of the main receiving direction of the antenna arrangement.
In this design, all the connections are still protected, since the electrical connections (which are normally formed on the lower face of the radome) for the supply cables are arranged to be stationary and fixed, and need not also be pivoted.
The pivoting in the azimuth direction can in principle be carried out manually. However, it is preferably carried out by a motor or motors.
Independently of the manual or motor adjustment about a vertical axis for different setting of the main beam direction in the azimuth direction, a different adjustment capability can also be provided in order to additionally vary the main beam direction in the elevation direction. In other words, the down-tilt angle can also be set differently, preferably electrically by means of different phase control of the antenna elements or antenna element groups which are arranged differently one above the other, as is known from the prior art.
Admittedly, in principle WO 02/27863 A1 and EP 1 175 741 disclose the provision of one or more antennas underneath a large protective housing, which is transparent for radio waves, with these antennas generally being offset with respect to one another in the horizontal direction and being arranged underneath the protective housing such that they can pivot. Protective housings in the form of domes are used for this purpose, underneath which the antennas are positioned such that they can be aligned. Protective housings such as these, which are generally provided for point-to-point antennas or for other specific directional antennas, have nothing in common with the specific subject matter of the application, however, which relates to a mobile radio antenna arrangement for a base station in which the radome generally surrounds the antenna element or antenna element groups, a short distance away from them and providing protection.